code: def _do_self_dots_subset(
      intrad,
      rmags,
      rlens,
      cosmags,
      ws,
      volume,
      lut,
      n_fact,
      ch_type,
      idx,
  ):
      """Parallelize."""
      # all possible combinations of two magnetometers
      products = np.zeros((len(rmags), len(rmags)))
      for ci1 in idx:
          ci2 = ci1 + 1
          res = _fast_sphere_dot_r0(
              intrad,
              rmags[ci1],
              rmags[:ci2],
              rlens[ci1],
              rlens[:ci2],
              cosmags[ci1],
              cosmags[:ci2],
              ws[ci1],
              ws[:ci2],
              volume,
              lut,
              n_fact,
              ch_type,
          )
          products[ci1, :ci2] = res
          products[:ci2, ci1] = res
      return products
  
file_path: mne-python/mne/forward/_lead_dots.py
imports: import os
  import os.path
  import numpy
  from numpy.polynomial import legendre
  from ..parallel import parallel_func
  from ..utils import _get_extra_data_path, fill_doc, logger, verbose
label_desc: Use image node_id 9 for calling a global function with example usage: _do_self_dots_subset(intrad, rmags, rlens, cosmags, ws, volume, lut, n_fact, ch_type, idx) and returns: products